An Air of Concern

April 1, 1999
Often, the problems that cannot be seen in school facilities are the ones that create the most difficulty. One such problem is the indoor air in classrooms,

Often, the problems that cannot be seen in school facilities are the ones that create the most difficulty. One such problem is the indoor air in classrooms, support spaces and other areas. According to the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE), poor indoor air quality (IAQ) is the result of contaminated materials generating particulate, gases and vapors in the indoor space by occupants and their activities in a space, or brought in from the outdoors. Unfortunately, often IAQ problems are hard to diagnose and cure.

Among the signs that a school facility has an IAQ problem are:

-Symptoms are widespread.

-Symptoms disappear after occupants leave school for the day.

-The onset is sudden after some change at school.

-People with allergies have a reaction indoors but not outdoors.

-A physician has diagnosed an individual with an indoor-air-related illness.

A number of suspects can lead to poor IAQ in schools. Among potential causes include:

-Drinking water. Lead in pipefittings from solder on copper fittings can result in problems.

-Air-handling equipment. Dirty filters or indoor ductwork, and restricted or plugged outdoor air-intake grilles from bird nests or other debris often are culprits.

-Fumes or emissions. Home-economics and science labs, machine and auto shops, and arts and crafts classes can generate heat and irritating fumes.

-Electromagnetic forces (EMF). Some people feel that EMF from power equipment has an effect on the human body.

-Gases. Radon from basements and tunnels, CO2 from fuel-burning equipment in science rooms, shops, kitchens, home-economics rooms and heating systems can result in problems.

-Cleaning materials for floors, carpeting and draperies. Mold, dust and dirt will create conditions that can attract insects, vermin and contaminants.

-Plumbing and plumbing vents. If not maintained properly, these can cause sewer gas to vent into the building.

-Plants and animals in classrooms. Airborne furs, dander or body fluids cause allergic reactions in some people. Repeated exposure also can cause sensitivity for certain people.

-Swimming pools. Because of their nature and the number of people using pools, these need extra care in cleaning to eliminate the possibility of germs and disease.

-Excessive moisture. In classrooms, this contributes to mold, mildew and other growths.

-Poor ventilation. Ventilation is the means by which stale indoor air is exhausted from the building, and outdoor air is brought into the building. If not sized properly or if flow is restricted, problems may occur.

-Comfort level. Temperature and humidity can affect IAQ. Changing a thermostat or sensor setting to control a temporary fluctuation, or opening windows to cool down a classroom, can cause IAQ problems in other areas of the building.

Understanding the problem The indoor environment in a building is the result of interactions among site, climate, structure, mechanical systems, construction, contaminant sources and occupants. These can cause IAQ problems, and are grouped into four categories:

-Sources. There is a source of pollution or discomfort, whether it be indoors, outdoors or in the mechanical system of the building.

-HVAC systems. The HVAC system is not able to control air pollutants and/or ensure thermal comfort.

-Pathways. One or more pathways connects the pollutant source to the occupant, and a driving force exists to move the pollutants along the pathway.

-Occupants. Occupant activities have a direct impact on sources, HVAC systems, pathways and driving forces, and occupants can be carriers of communicable diseases and allergens.

There are six basic control methods for lowering concentrations of indoor air pollutants. These include:

-Source management, including removal, substitution and/or encapsulation.

-Local exhausts, which remove the source of pollutants before they can disperse into the indoor air. Examples include kitchen and bathroom exhaust systems.

-Ventilation through the use of cleaner (outdoor) air to dilute the polluted indoor air building occupants are breathing.

-Exposure control, which includes planning the time and location of use of potential contaminants. An example of controlling exposure time would be to schedule stripping and waxing of floors on Friday after school, giving the weekend to vent or reduce the odor from the chemicals that were used. A location-of-use example would be to change the location of the work to another area, or relocate occupants to another area of the building.

-Air cleaning, which involves the filtration of particles from the air as it passes through the ventilation filter.

-Education of building occupants regarding IAQ. It is critical that staff and students understand the causes and sources of contaminants, and know how mechanical systems work in helping reduce contaminants.

Solving the problem To address an IAQ problem, develop a management plan and select an IAQ coordinator. The coordinator will gather all the information about the building, including lighting, radon, asbestos and any other item that could affect the building's IAQ.

A problem-solving checklist should be issued to a number of people in each area, (teachers, maintenance, clerical, custodial, administrators and others) for their input as to the location and type of problem. When the checklists have been completed and returned to the IAQ coordinator, the compiled data can be distributed to the IAQ team.

A walk-through to inspect items on the checklist and the facility is the next item on the agenda. During the walk-through, people can learn a lot by using their senses of sight, smell, touch and hearing. Individuals should:

-Observe the level of cleanliness while looking for pollutant sources.

-Smell for any unique and objectionable odors.

-Feel for uncomfortable air temperatures, drafts, high or low humidity, and feel airflow from grilles and diffusers.

-Listen to the concerns of the staff regarding IAQ. They may provide information to pinpoint a problem. Also, it is extremely important to communicate IAQ concerns with all staff.

After the walk-through, develop a repair and upgrade priority list with solutions for the recorded problems. Again, distribute copies of the list to occupants. Perform the repairs and upgrades, and then conduct a follow-up inspection. Remember, communication, response to problems and documentation are keys to a successful IAQ program.

Moisture is a key factor in the growth and amplification of mold, fungi and other microbes. As a result, problems with these organisms can be severe in air-conditioned buildings located in humid environments, especially in the southern United States.

The accumulation of moisture on or in the envelope of buildings in these climates is influenced strongly by indoor temperature and outdoor humidity. Mold growth typically occurs on internal surfaces of the external walls or floors, since these surfaces are cooled by the air-conditioning system to below or near the dewpoint temperature of humid air infiltrating the building envelope. Moisture enters the building because of:

-Leakage of rain into the wall cavities.

-Movement of humid air into the interior because of poor building construction.

-Water vapor diffusion from the humid exterior to the dry interior and, perhaps most common, entry through the conventional HVAC system when the supply air fan is operated while the cooling coil is cycled off.

Overcooling of indoor spaces results in moisture and mold problems in buildings in climates where the outdoor dewpoint temperature is at or above about 77 degrees F (25 degrees C). The problems can become severe when the internal surface temperatures drop a few degrees below 77 degrees F and the likelihood increases that the surface relative humidity will exceed 65 percent. Ironically, when building occupants feel clammy because of high space humidity, the typical response is to lower the space thermostat setting. The result is that the space cools further, most often increasing the space relative humidity, along with the likelihood of condensation of moisture on supply air ducts, floors and other building surfaces.

Moisture problems also can be a function of the occupancy load. High occupant densities, such as those in schools, generally result in a relatively high degree of moisture release into room air. When there is a combination of high occupant densities, poor ventilation and cold external walls, often moisture, dirt accumulation and mold growth occur in walls and on building surfaces. These can be controlled by proper ventilation with preconditioned (dehumidified air at room neutral temperature) outdoor air.

Although the symptoms below could be caused by conditions other than poor indoor air quality, such as improper lighting, poor ergonomics, or stress on the job or at home, the conditions are common to those who are experiencing difficulty in their environments:

-Headaches, fatigue and shortness of breath.

-Sinus congestion, cough and sneezing.

-Eyes, nose, throat and skin irritation.

-Dizziness and nausea.

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